The present invention relates generally to laser cutting of holes, and more particularly to apparatus and methods to trepan a plurality of holes into a cylindrical work surface.
It is common practice to use computer targeted lasers to drill holes into metal surfaces. Lasers are particularly useful in drilling holes into alloys of metal that are particularly tough to machine. One application is in aircraft turbine engines where multiple small diameter holes must be drilled, often at an angle, into tough alloy material.
U.S. Pat. No. 6,130,405 shows one prior art method of drilling holes using a laser. In the method of this patent the work piece is continuously rotated and a computer controlled laser punches holes into the work piece. Laser pulses are timed with the rotation of the work piece such that a row of spaced holes are created. U.S. Pat. No. 6,130,405 is limited to creating holes having a diameter equal to the diameter of the laser beam. This technique is useful in creating holes having a diameter in the range of 0.01 to 0.03 inches. However many of the holes required are going to have a larger diameter than is possible to cut with this method.
Another prior art example of laser cutting holes in a cylindrical work piece is U.S. Pat. No. 4,952,789 to Suttie. In the Suttie device, a laser L is used to cut a plurality of holes in a cylindrical work surface. Again, the diameter of the holes laser drilled in the work piece is determined by the diameter of the laser beam used for drilling.
U.S. Pat. No. 5,223,692 to Lozier et al. discloses a method of laser trepanning that can be used to cut a hole in a work piece having a diameter larger then the diameter of the laser beam. While the method of Lozier can be used to cut a larger diameter hole, it is very slow to use in applications where 100 or more holes can be spaced out in a row around a cylindrical work piece.
As can be seen, there is a need for an improved method and system of drilling holes in a cylindrical work surface using a laser. There is a need for a system and method that will allow for rapid cutting of holes having a diameter larger then the diameter of the laser beam used to cut the holes.
In one aspect of the invention, there is continuous movement between a work piece and a pulsed laser that sequentially trepans a plurality of holes arranged around the work piece. Each hole to be cut in the work piece is larger then the diameter of the laser beam, and requires a sequence of laser pulses targeted at its periphery to complete the hole.
In another aspect of the invention, a first series of small trepan cuts are made into the work piece, the laser is then targeted to the next trepan position and a second series of trepan cuts are made. The cuts in the first and second series of cuts are connected to form a portion of the periphery of a series of holes to be cut. Targeting to the next trepan position is done while the work piece continues to rotate from the last hole in the row back to the first hole in the row.
In a further aspect of the invention, a sensor detects that the cylindrical work piece is properly positioned relative to said laser prior to each laser pulse.
In a still further aspect of the invention, a programmable controller is used in a method to set the characteristics of the series of holes to be cut into the cylindrical work piece. Programmable steps include setting the hole angle, hole diameter, and number of holes to be cut. A hole can be cut normal to the surface of the cylindrical work piece, or a hole can be cut at an angle to the normal.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.